Space discharge tube construction



] Filed July 27, 1932 a Sheets-Sheet 1 V INVENTOR August Hunfl BY 7ATTORNEY Jl lly 17, 1934. HUND SPACE DISCHARGE TUBE CONSTRUCTION ssheets-Shea 2 Filed July 27, 1932 m Y T M m m Wm ,w l A WW H 8 5 0 m R QMUJH July 17, 1934.

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240 280 l/O/ZS 12 0 200 Work anode p0 zenf/a/ 5 d m R mH m E VLl m 0 2Eu M 0 m H n om I w 6 om 4H .r W W l I0 8 BY fi W "1. ATTORNEY PatentedJuly 17, 1934 UNITED STATES SPACE DISCHARGE TUBE CONSTRUCTION AugustHund, West Orange, N. J., assignor to Wired Radio, Inc.,' New York, N.Y., a corporation of Delaware Application July 27, 1932, Serial No.624,920

10 Claims. (Cl. 250-27.5)

This invention relates to glow discharge tubes and has particularreference to the structural details thereof and to the adaptation ofsuch tubes for a wide range of uses in electrical circuits generally.

An object of my invention is to provide a glow discharge tube of thischaracter comprising a plurality of electrodes of conformity suitable tothe peculiar manner of activating such tubes.

Another object of my invention is to provide a tube of the classdescribed which functions so as to exhibit a primary and a secondaryglow discharge, thereby rendering it suitable in a variety of circuits;for example, as in an oscillator, a del tector or an amplifier.

Another object of my invention is to so proportion the respectiveactivated areas of the electrodes and to envelop the electrodes in asuitable gas at a suitably attenuated pressure so that optimumconditions may be obtained for the operation of such tubes.

Another object of my invention is to provide a glow discharge tube ofthe class described, in which the electrodes are suitably disposed in aj medium of attenuated gas or mixture of gases so as to exhibit a highdegree of power gain between the input and output circuits of the tube,a minimum wattage consumption being required in the ionizing circuit, aswell as in the work circuit.

These and other objects are attained by a novel construction of the glowdischarge tube, as will be more fully understood from the followingdescription and by reference to the accompanying drawings, in which:

Fig. 1 depicts in elevation one embodiment of a glow discharge tubehaving its ionizing electrodes disposed internally of the work electrodesystem;

Fig. 2 is a sectional view of the electrodes along the line 2-2 of Fig.1;

Fig. 3 is an alternative embodiment of the glow tubes of my inventionshowing the ionizing electrodes disposed externally of the workelectrode system;

Fig. 4 is a plan view of the electrode system '1 shown in the tube ofFig. 3;

Fig. 5 shows a modified tube somewhat similar to that of Fig. 1, buthaving a work anode of cylindrically crimped formation;

Fig. 6 shows the work anode crimped in a plane; and

Figs. '7, 8 and 9 are curve diagrams illustrating some of the operatingcharacteristics of one of the glow tubes of my invention.

In my copending application, Serial No. 590,- 561, filed February 3,1932, I have shown several ionization electrodes independent of theother electrodes called work electrodes. The tubes of my invention asherein disclosed, while adapted to function in a similar manner, havecertain improvements of structural detail as compared with the tubes ofthe aforementioned application.

In my copending application, Serial No. 613,- 710, filed May 26, 1932,one of the uses of a tube of the class herein described and its mannerof operation in an oscillator circuit is illustrated. It will beunderstood, however, that these tubes may be used in a great variety ofdiiierent circuits for the achievement of new and desirable results.

The herein described tubes may be distinguished from those of myabove-mentioned copending application, Serial No. 590,561, in that theelectrodes are differently formed and otherwise characterized so as toset up a glow, or secondary ionization, in the region of the work anode,provided a suitable potential is applied to the latter.

My discovery, which resulted from the con-. struction and manner ofoperation herein shown, appears to go directly contra to previouslyaccepted theories, in that the operating characteristics of glow tubessuch as mine are greatly improved when this secondary ionization takesplace. In the space between the primary and secondary ionization acontrol electrode may be suitably disposed so that very considerablespace currents'passing toward the work anode may be controlled by a verysmall Voltage variation impressed upon the control electrode.

Referring now to Figs. land 2, a glow discharge tube is shown having asuitable envelope 1, and base 3 of well-known type. The severalelectrodes of the tube are connected by leads 4 with the prongs 5.The'leads are suitably insulated as by the'glass tubes 6, so as toprevent the possibility of ionization in unwanted regions.

In the embodiment of my invention as shown in Fig. 1, there are providedan ionizing cathode '7 and an ionizing anode 8, each of which consistspreferably of one or more convolutions of a simple wire helix. In placeof the helix construction, however, it is within the scope of'theinvention to employ either solid or hollow cylinders or-electrodeshaving other suitable shapes. In general, however, the eifective workingarea of the ionization cathode 7 is usually greater than that of theionization anode 8. This area relationship provides the advantage thatan excess of negatively charged ions and electrons is available at theionizing cathode 7 for building up the space current toward the workanode 10. This space current may then be suitably modulated as it passesthrough the mesh of the control electrode 9, when variations ofpotential are applied to the latter. I v

A preferred form of control electrode 9 is that of a simple wire helix.The work anode 10 may, if desired, be a round or flat wire ring and itslocation is found to be satisfactory when the plane of the ringsubstantially bisects the working area of the cathode 7.

As shown in Fig. 1, each of the electrodes is of' circular formation andthey are arranged concentrically with respect to one another.

Referring now to Figs. 3 and 4,- the embodiionizing cathode'll and theionizing anode 12.

This ionization, however, ismore or less localized in those regionswhere thebends in the anode 12 approach the cathode ll. Theeffectiveworking area of the cathode 11 is, therefore, greater 1 than that of theanode l2 notwithstanding the fact that the two rings have substantiallythe same diameter and an even greater developed length of wire is usedin the anode 12 than in the cathode 11.. Due to this construction;therefore, it is possible toset up a stream of negatively charged ionsand electrons in the region of, primary glow discharge, which stream iscentripetally projected through the mesh of the control electrode 14 andtoward the centrally disposed work anode 13, where secondary ionizationtakes place Y The results obtained from the operation of the tube asshown in Figs. 3 and 4 are comparable with those hereinbefore describedwith respect to Figs. 1 and 2. The operation ofboth tubes will,therefore,'be understood in View of the foregoing description. 7

Referring now toFig. 5, a third modification of my invention is shownwherein the ionizing electrodes 7 and 8 are centrally disposedandsurrounding them is the control electrodeQ, ,the same as shown inFig. 1. In this embodiment, however, a crimped formation of the workanode l5is provided. The zig-zag pattern may becylindrically crimped asshown in Fig. 5, or, alter-- natively, it' may conform to .aqplane as inFig. 6.;

In the embodiments of my invention shownin Figs. 1 2, 5 and 6, primaryionization takes place as before mentioned between the centrally-diswposed ionizing electrodes, whence streams .of

negativelycharged ions and electrons are centrifugally projected throughthe mesh of -t he'control electrode and toward the outwardly disposedwork anode 10, 15 or 16, as the case maybe. Secondary ionization takesplacev in allcases, in the region of the work anode. The operation ofthe tubes of these. modifications .is, therefore, similar to that ofthetube embodiments previ-, ously described.

In order to illustrate some of .the operating .the curves of Figs. 7, 8and 9 were plotted, the 'gas within the envelope was nitrogen at apressure of 24' mm. mercury. Across the ionizing electrodes was a dropof 308 volts with an ionization current of 35 mill'iamperes. Theionization power was, therefore, only 10.8 watts.

Fig. 7 shows the relation between the workanode potential and thework-anode current when a bias E3 of 27 volts is impressed uponthe'control electrode with respect to the potential-of the positiveionization electrode. Due to the scale on which the currentvariationswere plotted, the curve appears to start at O and ascends very slightlyto the point a. Careful measurements, however, showed that, with noexternal voltage applied between the work anode and the positiveionization electrode, a minute flow of current could be observed whichapparently is dueto the primary ionization pressure (or spill) towardsthe work anode. This minute currentis comparable in magnitude with thatcustomarilyfound in thermionic tubes when the plate is directlyconnectedto the filament, i. e., without plate battery. It. is of; nosignificance in the ordinary uses of these ,tubes. 1

At about 84 volts of workanode potential the current curve jumpssuddenly between the points a and b; thatis, approximately from 0.25 to3.8 m.,a. This is due to the commencement of a secondary glow dischargein the region of the work anode. With further increases .in thework-anode potential, the. work-anode current increases rapidly up tothepoint d, wherea streamer dis chargesets in between-the work anode andthe control electrode. The unstable condition of the tube between a andb, and again, the streamer discharge above the point (2 determine theuseful ranges for operating thetube as anordinary detector or amplifier.The useful ranges are-between 1) and (1, also between 0 and a. Theformer is much to be preferred, however, since it is possibleto controlso much more output power with a given fluctuation of input potentialapplied to the control electrode.

NVhere the tube is intended to function as a threshold amplifier or triprelay, the operating characteristic ,inay be swung over the range whichstraddles the critical points a and b or else above the point d, so thata large current may trigger off withvery slight variation in the controlpotential.

Fig.8 shows a number of curves corresponding withthatof Fig. -..'7,i buton an enlarged scale and confined to the normal operating range b'-d..Thedifferent curves were obtained underlthe conditions of controlelectrodebias as shown. The dot-and-dashline runningthrough theoperating point'c indicates the region in which the best operatingconditions prevail. "It is near the region of saturation and not farfrom the region of streamer-discharge d.

The extraordinarypower gain which results from-operating'these tubes inthe manner shown will be. betterunderstood when it, is .considered thatthe primary flow of negative ions passing through the mesh of thecontrol electrode is increased many fold by the production of new andadditional ions as the stream approaches the work anode. Thus, thecurrent flowing towards the work anode is greatly increased by virtue ofthe secondary ionization and with no need for a corresponding increasein the input power applied to the control electrode.

As was brought out above, streamers set in at the point at. Beyond thispoint the control electrode becomes flooded with a streamer glow and thetube can no longer function as an amplifier of voice and carriercurrents. Many experiments were therefore carried on to shift the pointd as far out on the characteristic as possible.

It may be of interest to note here that success in this direction didnot result from attempts to completely surround the control electrode,as by a hollow cylinder. The reason for this was that streamers would beset up between the cylinder wall and the control electrode even whenvery low voltages were applied between the work anode and the ionizationanode. Hence the round wire or fiat metal ring shaped work anode 10, orthe crimped wire work anode l5 and 16 were found to be preferable, asthey tend to move the point 11 practically into the saturation region,thus providing a very powerful output. Substantially the same advantagealso accrues from the use of an axially disposed work anode 13, as shownin Fig. 3. For some purposes, however, the wavy ring construction asshown either in Fig. 5 or Fig. 6 is to be preferred.

Fig. 9 gives curves for the control electrode current in relation to thework anode potential. This diagram, when considered in connection withthe curves of Fig. 8, provides the means for computing the dynamic plateresistance Tp, the mutual conductance gm, the amplification factor andthe dynamic input resistance Tc.

The load line may be drawn as shown in Fig. 8, passing through theoperating point e, and at such an inclination as to avoid distortion inthe amplified output current variations. Furthermore, this load linedoes not extend beyond the streamer points of the several characteristiccurves plotted for different control electrode potentials.

The computations show that the dynamic resistance is as low as 5420ohms, while the amplification factor ,u. for this particular tube is ashigh as 20.65. Hence the mutual conductance gm is as high as 3815. Withsome of my tubes it is an easy matter to produce a mutual conductance ashigh as 10,000. Some of my tubes have an amplification factor a as highas '70 or 80, the dynamic plate resistance being not greater than 10,000ohms. With a tube of this type, therefore, a very high degree of poweramplification is obtainable, while preserving a very low dynamic plateresistance along with a high dynamic input resistance. A furtheradvantage to be had in these tubes is the avoidance of the necessity foradding another control electrode such as found in the so-called pentodetubes for producing a low output resistance.

I claim:

1. A gaseous discharge tube comprising an ionizing cathode, an ionizinganode the activated surface of which is relatively smaller than that ofsaid cathode an output circuit anode for localizing a glowing ionizationdischarge in a region other than that in which ionization is produced bysaid ionizing cathode and anode, and an openly constructed controlelectrode interposed between the two regions of ionization, said outputcircuit anode being of a crimped ring formation surrounding said otherelectrodes.

2. A gaseous discharge tube comprising an ionizing cathode of closelywound helical formation, an ionizing anode the activated surface ofwhich is relatively smaller than that of said cathode, an output circuitanode for localizing a glowing ionization discharge in a region otherthan that in which ionization is produced by said ionizing cathode andanode, and an openly constructed control electrode interposed betweenthe two regions of ionization.

3. An electrical discharge tube comprising a plurality of electrodesenveloped in an attentuated gas two of said electrodes being suitablypositioned for setting up a primary ionization discharge therebetween,an output circuit anode suitably arranged to localize a secondaryionization discharge therebetween and a control electrode interposedbetween the regions of primary and secondary ionization respectively,said output circuit anode being of crimped ring formation surroundingthe other electrodes.

4. An electrical discharge tube comprising a plurality of electrodesenveloped in an attenuated gas, one of said electrodes being an ionizingcathode, another of said electrodes being an ionizing anode, said twoelectrodes being suitably positioned for setting up a primary ionizationdischarge therebetween, said ionizing cathode being of closely WOlllldhelical formation, a third electrode being suitably arranged to localizea secondary ionization discharge thereabout and a control electrodeinterposed between the regions of primary and secondary ionizationrespectively.

5. A gaseous discharge tube comprising a pair of ionizing electrodes, anopenly constructed control electrode externally disposed with respect tosaid ionizing electrodes, and means including an output circuit anode ofcrimped wire ring formation for localizing a glowing ionizing dischargeexterior to said control electrode.

6. A gaseous discharge tube in accordance with claim 5 in which saidoutput circuit anode is crimped so as to conform substantially to acylindrical surface.

'7. A gaseous discharge tube comprising, a pair of ionizing electrodes,an openly constructed control electrode operatively disposed withrespect to said ionizing electrodes, and means including an outputcircuit anode of crimped wire ring formation for localizing a glowingionizing discharge adjacent said control electrode.

8. A gaseous discharge tube in accordance with claim '7 in which saidoutput circuit anode is crimped so as to conform substantially to acylindrical surface.

9. A gaseous discharge tube comprising a plurality of electrodesenveloped in an attenuated gas, two of said electrodes being ionizingelectrodes and another a control electrode operatively related to saidionizing electrodes and one of said plurality of electrodes being in theform of a crimped ring encircling said control electrode.

10. An electrical discharge tube comprising an envelope containing anattentuated gas, a plurality of electrodes within said envelope betweencertain of which a space current may be established, a control electrodeoperatively related to said space current electrodes and one of saidplurality of electrodes being in the form of a crimped ring surroundingsaid control electrode.

AUGUST HUND.

